Endocrine Abstracts

Background: According to American Thyroid Association guidelines, hyperfunctioning thyroid nodules do not require cytology due to the low risk of malignancy [1]. Papillary thyroid carcinomas from the isthmus are rare with an incidence of 1.0-9.2% [2].

Case Report: A 26-year-old male presented with a 9-month history of hyperthyroidism, previously treated with carbimazole 15 mg/day. He had a strong family history of autoimmune thyroid disease; his mother had hypothyroidism and his brother was diagnosed with Graves’ thyrotoxicosis. TSH receptor antibody was negative, TPO antibody 95 KIU/L (0-34), FT3 5.3 pmol/l, FT4: 16.0 pmol/l, and TSH: 2.3 mIU/ml while on antithyroid treatment. Initial thyroid ultrasound revealed multiple <5mm hypoechoic foci representing pseudonodules /spongiform nodules in both lobes (U2). On the right side of the isthmus was a bulging, well-defined, hypoechoic, solid 1.6 x 0.9 cm nodule, lobulated margins, trace peripheral vascularity, without microcalcifications (U2). There was no cervical lymphadenopathy. Based on these findings, carbimazole treatment was continued and routine follow-up ultrasound planned. On repeated ultrasound at 1 year, the isthmic nodule’s dimensions were unchanged at 1.6 X 0.9 cm but due to interval change of microcalcifications and extrathyroidal extension, the nodule was re-stratified U3. Fine needle aspiration revealed features of papillary carcinoma. Total thyroidectomy was performed; histopathological examination confirmed a papillary thyroid carcinoma of classic type 1.7 x 1.5 cm; the excision margins were free of carcinoma and the specimen negative for lymphovascular or perineural invasion; background appearances were of chronic lymphocytic thyroiditis; no local nodal disease was detected. Post-procedure, thyrotoxicosis resolved and serum thyroglobulin was undetectable.

Conclusion: Papillary thyroid carcinoma is sporadic in the context of hyperthyroidism at presentation. In this case, scintigraphy assessment was impeded due to established carbimazole therapy at a relatively high maintenance dose. Routine ultrasound follow-up and re-evaluation were critical to accurate diagnosis and early treatment.